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Title: Mechanisms and sources of predictability in the North Pacific Basin during the 1980s & early 1990s
Author: Webster, Jason Riley
Awarding Body: University of Reading
Current Institution: University of Reading
Date of Award: 2013
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This thesis investigates causal mechanisms and predictability of North Pacific decadal variability in the 1980s and early 1990s. Observations and proposed mechanisms of North Pacific decadal variability are reviewed. A significant warming of central North Pacific Ocean surface and subsurface was identified and shown to be predictable up to six years lead-time in the United Kingdom Meteorological Office Decadal Prediction System (DePreSys). The possible role of the April 1982 El Chich6n volcanic eruption in North Pacific Ocean cooling prior to the warming is investigated using climate model experiments. El Chich6n significantly weakens the East Asian Summer Monsoon and enhances the East Asian Winter Monsoon through modification of the land-ocean temperature contrast between East Asia and the western North Pacific. East Asian Monsoon changes cool the western North Pacific for up to three years through enhancement of cloudiness in summer and latent heat flux in winter. The resulting cooling enhances the magnitude and persistence of central North Pacific Ocean cooling. North Pacific atmospheric variability during the late 1980s and early 1990s was persistently anticyclonic and equivalent barotropic. A sensitivity experiment finds anomalous turbulent surface heat and momentum fluxes, resulting from anomalous anticyclonic atmospheric conditions, force the central North Pacific Ocean warming. This warming is related to a poleward displacement of the subtropical gyre resulting from anomalous Ekman pumping. A sensitivity experiment investigates the role of North Pacific, North Atlantic and Tropical sea surface temperatures as the predictability source of persistent anticyclonic tropospheric conditions over the North Pacific. Winter 1988/89 anticyclonic conditions are the result of a concurrent La Nina. A multi-year anticyclonic persistence mechanism is not identified. Recommendations for future investigations of the late 1980s and early 1990s warming, the East Asian Monsoon volcanic eruption response, and decadal climate prediction are presented.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available